Magnetostrictive transducer apparatus



March 9, 1965 R. c. HEIM MAGNETOSTRICTIVE TRANSDUCER APPARATUS Filed Jan. 31, 1963 2 Sheets-Sheet 1 L Fi .l.

INVENTOR WITNESSES 94% Richard C. Heim March 9, 1965 R. c. HEIM MAGNETOSTRICTIVE TRANSDUCER APPARATUS 2 Sheets-Sheet 2 Filed Jan. 31, 1963 P OW ER SUPPLY Fig.4.

United States Patent poration of Pennsylvania Filed Jan. 31, 1963, Ser. No. 255,246 Claims. (QB, 316-26) The present invention relates to magnetostrictive transducer apparatus of the type suited for vibrating a liquid medium to improve cleaning operations, form emulsions, homogenize liquids, etc.; and more particularly to improvements in such a transducer apparatus as is disclosed in copending US. patent application Serial No. 223,305, filed September 11, 1962, as a continuation of copending US. patent application Serial No. 722,817, filed March 20, 1958, now abandoned, employing a highly-efiicient array of thin space-separated magnetostrictive elements, or so-called laminations, distributed over substantially the entire liquid-exposure area of a radiating plate which couples the ends of the magnetostrictive elements vibrationally to the liquid without significant bending of the plate between elements and loading of the elements by the mass of the plate, to alford matching the impedance of the magnetostrictive elements to the impedance of a depth of liquid contained in a tank or vessel.

In such previous apparatus of the identified patent ap plication, spacers were employed to obtain the desired space separation between the magnetostrictive elements and each element had a window or opening which was aligned with corresponding windows in a linear array of the elements to accommodate the windings of a coil for energizing all elements of such array.

While entirely satisfactory from the standpoint of performance, such structural features introduce an element of complexity with respect to fabrication of the apparatus which becomes reflected in the cost both as to labor and material. For example, the aligned coil-turn-accommodating windows necessitates the forming of the coil while it is introduced to the array, by threading each turn through these windows and this dictates the use of rela tively-expensive multi-strand wire in order to satisfy the initial flexibility requirement. Furthermore, multi-strand wire of limited cost, such as Class A, presently is coated with a plastic insulating material of such temperaturewithstanding limitation as to have required the use of a small fan or blower in such previous apparatus in behalf of assuring integrity of such material during prolonged periods of operation.

In accord with the present invention, improved features of the transducer apparatus include: the use of magnetostrictive elements which are self-spacing, as by inclusion of portions on each element which abut corresponding portions on adjacent elements while affording the desired degree of distributed space-separated end area contact of such elements with the radiating plate of the apparatus; the use of open-ended coil-accommodating slots extending from the free or non-radiating-plate end of the elements, rather than windows, to enable the energizing coil to be prewound on a coil winding machine and readily inserted into and removed from the accommodating recess formed by a series of such slots when aligned in a space-separated array of the improved magnetostrictive elements bonded at their opposite ends to the radiating plate; and the use of such a prewound coil in compatability with such coilaccommodating slot feature and which coil may be fur ther distinguishable by the use of the Well-known relatively low-cost, durable, enameled magnet wire, Class H, for example, which will withstand temperatures up to 200 C. and obviate need for forced air cooling of the apparatus.

These and other features of the invention will become apparent from the following detailed description in connection with the accompanying drawings in which:

FIGURE 1 is a view in outline of one face of the improved magnetostrictive element employed in plurality in the transducer apparatus of the present invention;

FIG. 2 is a view in outline showing the ends of a number of the improved magnetostrictive elements when assembled in abutting, self spacing, relationship in a linear array;

FIGURE 3 is a three-dimensional cut-away view in elevation of the improved magnetostrictive transducer apparatus as embodied in a liquid-holding tank for such as ultrasonic cleaning purposes involving cavitation of the liquid medium with the tank; and

FIG. 4 is a bottom view of the transducer assembly as including two linear arrays of the improved magnetostrictive elements, including the performed energizing coils, as bonded to the underside of the radiating plate.

Referring to FIGS. 1 and 2 in the drawings, the improved magnetostrictive element 1 as exemplified herein is made of thin-sheet magnetostrictive material, such as Grade A nickel .005 inch thick, which is shaped, as by stamping, to provide two spaced-apart, open-end, rectangular coil-accommodating slots 2 extending longitudinally from one end, which end is frequently the bottom end where the upper end is bonded to the underside of a radiating plate 3 which constitutes the bottom of a tank as in FIGS. 3 and 4. Preferably the length of element 1 is onehalf the wavelength of the high frequency electrical energy source; this is approximately four and one-eighth inches for grade A nickel at a twenty kilocycle energizing frequency. A successful experimental configuration of the shape exemplified in FIG. 1 employed an overall width of approximately two and fifteen sixteenth inches, with the two slots 2 symmetrically arranged, about three and fivesixteenths inches long, about five-eighths of an inch wide, and separated about seven-eighths of an inch. At each edge of each slot 2 there is provided a corrugation to atford a spacing ridge 5 which is offset perpendicularly from planar areas 6 in the vicinity of the slots 6 at the extreme edges, and in the middle. This offset was about one-sixteenth of an inch in the experimental configuration. Each ridge 5 is joined at one edge to the planar areas 6 at a perpendicular rib 7 and at the opposite edge by a sloping rib 8, which in the experimental configuration extended at an attitude of thirty degrees with respect to planar surfaces 6 and was one-eighth of an inch wide.

In assembly of the magnetostrictive elements 1 for bonding at their one end to one face of the radiating plate 3 the elements are stacked as in a rectangular frame for abutting contact between their respective spacing ridges 5 with such ridges on any two immediately-adjacent elements extending thicknesswise in opposite directions, as can be seen in FIG. 2. This gives a distributed spacing of dual-arranged thin edge areas of the magnetostrictive elements such that the total edge area of such elements relative to the area of the radiating plate 3 over which such end area is distributed is within the limits one-half to one and one-thirtieth to one for a radiating plate 3 of stainless steel having a thickness of from ten thousandths of an inch to one quarter of an inch, or equivalent in rigidity and mass of other suitable material. With such end area distribution of five-thousandths inch thick nickel magnetostrictive elements spaced-apart in dual abutment by one eighth of an inch, bonded to the bottom of a oneeighth inch thick stainless steel radiating plate 3 as the bottom of a cleaning tank containing six inches of water, distributed over substantially the entire liquid exposure area of such plate, and energized at a frequency of twenty kilocycles has operated with -a high degree of overall efiiciency.

As so stacked and self-spaced in a frame, the spaceseparated and distributed ends of the stacked ridgeabutting magnetostrictive elements, opposite to the slot 2 ends, are bonded to the radiating plate 3 by brazing such as an epoxy adhesive. This may be repeated, according to the size of the radiating plate 3, to give a dual array as in FIGS. 3 and 4, or greater number where necessary, to obtain the preferred full coverage of the liq11id-cxposure area of such plate.

Following the bonding of such an array of elements 1 to the radiating plate 3, an oval-shaped insulating member and coil mount 10 of V-shape in cross-section is inserted in the slots 2 of a particular array so as to extend between such slots at their opposite ends. Next a preformed energizing coil 11 of such as Grade H enameled magnet wire is inserted into the slot 2 and nested in the coil mount 10. Both coil 11 and mount 10 are held in place within the array of elements 1 by suitable retaining means 29 so as to be held in'place during a common attitude of the transducer assemblage, as in FIG. 3, where the slots 2 open downwardly.

Each coil 11 in each array is preferably energized by a common source of alternating current power, as in FIG. 4, and for the design parameters exemplified herein, this is preferably about twenty kilocycles per second.

The radiating plate 3 oftimes will be provided with upwardly extending walls 14, as in FIG. 3, to compose a tank for containing such as a liquid cleaning medium; the plate 3 serving as the bottom of the tank. In order to take full advantage of the invention, the space separated end areas of the magnetostrictive elements should be distributed over substantially the entire area of the bottom plate 3 within the domain of the tank walls 14.

While the slotted configuration for energizing coil accommodation of the present invention does not afford a complete flux path of magnetic material around the coil 11 due to the open end of the slots 2, it has been found that the magnetic flux associated with operation of the magnetostrictive elements of the transducer is carried by the air gaps at the open slot ends, with no significant change in eilective permeability of the magnetic circuit relative to the previous window accommodation of the coil. The number of turns of electrical winding of the coil required for driving and biasing the elements and for matching the electrical impedance to the transducer were the same as previously required for the coil-accommodating window-type elements, and electro-acoustic efiiciency also remained as high as aflorded in such previous window-type elements.

While the ridges of the magnetostrictive elements it afford the particular self-spacing feature of the invention, such ridges along the length of the elements also add stiffness and rigidly to the elements and to the transducer assembly.

Although an exemplification of the invention has been described with a degree of particularly, it will be understood that the invention is not necessarily so limited and that it is intended that the invention as defined by the appended claims is of a spirit and scope which embraces obvious modifications of such exemplification which would readily be apparent'to those versed in the art.

Having now described the invention, I claim:

1. A transducer assemblage comprising a plurality of thin magnetostrictive elements vibratorily coupled at their one end to a radiating plate, said elements having longitudinally-extendingcorrugations with their ridges in backto-back abutting relationship to afford distribution of such elements on said plate in a self-spacing space-separated relationship, said elements also having respective aligned slots extending longitudinally inward from their opposite ends; and a prewound energizing coil extending through said slots.

2. A transducer assemblage as set forth in claim 1, wherein the dimensions of such magnetostrictive elements are such as to give an end area of such elements of from one-half to one thirtieth of the area of said radiating plate over which such elements are distributed.

3. A transducer assemblage comprising a radiating plate, a plurality of parallel-arranged magnetostrictive elements each bonded at its one end to said radiating plate and having two parallel-arranged slots extending longitudinally from its opposite end, the slots in each element being aligned with the corresponding slots in the other elements to form two parallel troughs, and a preformed coil nested in said troughs, such troughs and coil being so constructed and arranged to permit insertion and removal of said coil While remaining intact as a coil.

4. A thin vibratory element of magnetostrictive material having one edge for bonding to a radiating plate, and having corrugations extending perpendicular from such edge longitudinally along said element, each of said corrugations in cross-section having a flat ridge for abutting engagement With a corresponding fiat ridge on an adjacent lamination bonded to the same radiating plate, an end rib at one ridge edge extending perpendicularly therefrom, and a sloping rib extending angularly of said other ridge edge.

5. A vibratory element as set forth in claim 4, wherein said element comprises two parallel-arranged slots extending longitudinally thereof from an edge opposite to its aforesaid edge to be bonded to a radiating plate, said slots being constructed and arranged for alignment with corresponding slots in other vibratory elements bonded to such plate to accommodate disposition of an energizing coil which may be preformed and inserted and reioved from such slots while intact as a coil.

References Cited by the Examiner UNITED STATES PATENTS 2,421,263 5/47 Herbst 34O----ll 2,9303 l 2 3/60 Miller. 2,957,994 16/60 Dickey 31026 MILTON O. HIRSHFIELD, Primary Examiner. 

1. A TRANSDUCER ASSEMBLAGE COMPRISING A PLURALITY OF THIN MAGNETOSTRICTIVE ELEMENTS VIBRATORILY COUPLED AT THEIR ONE END TO A RADIATING PLATE, SAID ELEMENTS HAVING LONGITUDINALLY-EXTENDING CORRUGATIONS WITH THEIR RIDGES IN BACKTO-BACK ABUTTING RELATIONSHIP TO AFFORD DISTRIBUTION OF SUCH ELEMENTS ON SAID PLATE IN A SELF-SPACING SPACE-SEPARATED RELATIONSHIP, SAID ELEMENTS ALSO HAVING RESPECTIVE 